Modern data centres typically house multiple rows of equipment cabinets standing on a raised access floor that serves as a pressurised air plenum to deliver cooling air to the computer equipment. The cabinet rows face onto “cold aisles” fed with cooling air from floor-mounted air grilles, and this is drawn through the equipment racks and discharged into “hot aisles” at the rear of the cabinet rows, where it is re-circulated via the computer room air conditioning plant.
Much of the cabling to the equipment racks is fed from the sub-floor space through holes in the floor deck/sub-floor. Cables are regularly added and removed, so large holes are required to provide ready accessibility, but these can leak substantial quantities of cooling air which will bypass the equipment racks and reduce cooling efficiency. To address this problem, seals have been developed that can be easily removed and replaced and which substantially reduce air leakage and thus increase the quantity of air delivered into the cold aisles. Such seals however offer virtually no resistance to fire. Whilst there are currently available fire-resistant seals, these are rigid and unadaptable to different sizes and numbers of cables, and are thus unsuited to applications where regular wiring changes are required.
Fire in data centres is a serious issue. The high rate of air flow in the sub-floor plenum will fan the development and spread of fire, which can then pass via floor penetrations into the equipment racks, with potentially catastrophic consequences.
To address this risk data centres are fitted with very early smoke detection apparatus, and rapidly deployable fire suppression systems in the form of water sprinklers and/or gas flooding systems. To be effective, the fire detection and suppression systems are set to activate at the first possible indication of a fire, and this creates an alternate risk of a false alarm which will unnecessarily activate the fire suppression and shut down the data centre; which is in itself a disruptive and costly event.
A further risk to electronic equipment comes from air-borne particulates, which may include zinc whiskers detaching from sub-floor structure, but also corrosive decomposition products resulting from fire, and accordingly a more effective barrier to air flow would also assist in reducing such hazards.
While the prior art addresses some of the issues, none are entirely satisfactory. Sempliner U.S. Pat. No. 6,632,999 discloses brush-seal devices in which multiple layers of opposing brushes spread around the cables from opposite sides of the grommet frame and thus shroud the opening. The seals are designed for easy removal and replacement to allow changes to cabling, and the seals are adaptable to different sizes and numbers of cables, however if the transiting cables pull sideways against the brushes the seal can open up and lose effectiveness.
U.S. Pat. No. 7,507,912, also to Sempliner, addresses issues of air leakage, electrostatic build-up and adaptability. Although mention is made of flame-retardant materials and alternative sealing elements made from flexible materials such as foam, there is no disclosure of practicable means to utilise such materials to achieve dust or water tightness, or fire resistance.
U.S. Pat. Nos. 7,544,901, 7,282,650 and 7,723,622 describe closures with more effective sealing capability, but these devices generally require the seal face to be profiled to suit a pre-determined conduit diameter, and so they are unadaptable to different conduit sizes and numbers. They also require effort to install and remove and so are unsuited to situations of constant cabling changes, particularly in confined spaces such as on the floor of equipment cabinets.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.